Acoustic noise attenuating apparatus



June 18, 1968 D. R. WILSON ACOUSTIC NOISE ATTENUATING APPARATUS Filed March 31, 1966 TRANSDUCER igure 2 INVENTOR.

DONALD R. WILSON BY ape-W ATTORNEY United. States Patent Olfice 3,388,767. Patented June 18, 1968 3,388,767 ACOUSTIC NOISE ATTENUATING APPARATUS Donald R. Wilson, Santa Cruz, Calif., assignor to Pacific Plantronics, Inc., Santa Cruz ,Calif., a corporation of California Filed Mar. 31, 1966, Ser. No. 539,092

2 Claims. (Cl. 181-31) ABSTRACT OF THE DISCLOSURE A noise-reducing adapter for an acoustic tube is disposed to couple acoustic energy from a source to a remote acoustic transducer and includes an acoustic attenuator for reducing the level of background noise and increased voice signal to the level of voice signal coupled to the acoustic tube in the absence of the adapter.

The main object of the present invention is to provide a background noise-reducing adapter for the acoustic coupling tube of a miniature microphone of the type which is disposed away from the speakers mouth.

In accordance with the illustrated embodiment of the present invention, a cup-like adapter is positioned at the mouth end of an acoustic coupling tube close to the speakers mouth. The adapter includes an internal acoustic canal which communicates at its inlet end with the cup-like portion of the adapter and at the outlet end with the acoustic coupling tube of the microphone. The inlet end of the acoustic canal is coupled to the cup-like portion through a porous element and the outlet end is coupled to the acoustic tube through acoustic attenuator elements.

Other and incidental objects of the present invention will be apparent from a reading of this specification and an inspection of the accompanying drawing in which:

FIGURE 1 is a perspective view of the adapter on the present invention attached to the acousticcoupling tube of an acoustic transducer; and

FIGURE 2 is a side sectional view of the adapter showing its internal construction.

Referring to the perspective and side-sectional views of the adapter shown in FIGURES 1 ani 2, there is shownan adapter body 9 having a generally cupped portion 11 and an internal bore 13 at the end of the adapter body remote from the cupped portion 11. The dimensions of the internal bore 13 are selected to snugly receive the end of the acoustic coupling tube 15 which is remote from the end coupled to transducer 17. Transducer 17 may be a microphone which produces an electrical output in response to applied acoustic signals. An acoustic canal 19 within the body 9 has an inlet port 21 which communicates with the cup portion 11 at an inner surface region thereof and which-is covered by porous element 23. One or more acoustic attenuator elements 25 are disposed at the outlet end of the acoustic canal 19 where it communicates with the internal bore 13.

When operating the transducer (e.g. a microphone) under normal conditions, the transducer is positioned adjacent the speakers ear or temple region, as by attachment to an eyeglass frame or by clip over the head or around the ear. The end 14 of the acoustic coupling tube 15 is then disposed near the speakers month without the adapter body 9 attached to tube 15. Acoustic energy is thus coupled from the speakers mouth to the remote transducer 17v along coupling tube 15. However, when operating the transducer 17 in areas of high-level background noise, the speakers voice signal may be lost in the background noise which is coupled to the transducer 17 along with the speakers voice. 6

According to the present invention, the adapter body 9shown in FIGURE 2 is then slipped-onto the end 14 of the coupling tube 15, as shown in FIGURE 1, with the cupped portion 11 closely disposed in front of the speakers month. By a capturing effect, the cupped portion increases the amount of voice signal coupled into tube 15 and hence increases the level of the voice signal emanating from the small area of the speakers mouth relative to the background noise level in the same region covered by the cupped portion 11. The acoustic energy including voice signal and background noise components in the region of the cupped portion 11 is coupled through inlet port 21 of canal 19 and acoustic attenuator element or elements 25 to the coupling tube 15 and, in turn, to transducer 17. The voice signal in coupling tube 15 is thus attenuated by elements 25 to about the level which normally occurs without adapter body 9 in place but, more importantly, the background noise level is also attenuated by the same amount. Thus, noise ratio of voice signal level to background noise level in coupling tube 15 is improved with the adapter 9 in place by an amount approximately equal to the attenuation factor of the elements 25. These elements 25 typically yield about 10 db reduction of background noise level below voice signal level and may be wafers of sintered metallic particles or other suitable acoustic resistance material having a total thickness of about 3 to 8 hundredths of an inch. Acoustic attenuators of thicker dimension and providing attenuation of approximately 20 db may be used in cases of extremely high background noise level. The porous element 23 which covers inlet port 21 of canal 19 aids in reducing the acoustic hissing sounds produced by certain consonants spoken into the closely disposed cupped portion 11 of the adapter body 9. This porous element may be a wafer typically about one-sixteenth of an inchthick of polyurethane open-cell foam having about pores or cells per linear inch of sound path through the wafer.

Therefore, the apparatus of thepresent invention provides a simple, passive means for reducing undesirable background noise well below the level of desired audible signals coupled to a microphone or similar transducer.

I claim:

1. A noise-reducing adapter for use with an acoustic transducer which is worn by a speaker and which has an acoustic coupling tube with an input end that is normally disposed away from and to the side of the speakers mouth, the adapter comprising:

an elongated body having an internal bore at one end which is capable of receiving the input end of an 7 acoustic coupling tube in operable engagement with said body;

the body including an inwardly concaved cup portion near the other end of the body remote from said one end;

an acoustic energy passage of smaller bore than said internal bore extending substantially lineally from said internal bore at one end to said inwardlyconcaved cup portion near the other end for acoustically coupling the internal bore to the cup portion; and

an acoustic energy attenuator element disposed in said internal bore adjacent the transition to said smaller bore of the acoustic energy passage for attenuating acoustic energy passing therethrough to enhance the ratio of the speakers voice signal to background noise coupled to a remote acoustic transducer.

2. A noise-reducing adapter as in claim 1 wherein:

said acoustic energy passage extends substantially axially in line with said internal bore and communicates in acoustic energy coupling relationship with the in- Wardly concaved cup portion substantially at the innermost recess thereof; and

said inwardly concaved cup portion is disposed with a normal to the surface of the inwardly concaved cup portion near the innermost recess thereof at an acute angle with respect to said passage, whereby said body extends the acoustic energy passage of an acoustic tube having an input end disposed away from and to the side of a speakers mouth to a position substantially directly in front of the speakers mouth.

References Cited UNITED STATES PATENTS Olney et al.

Dreher et al.

Kishi et al. 181 --31 Caldwell.

Behymer et al.

Knutson et al 18131 Stryker 181-50 Wilson 181-31 RICHARD B. WILKINSON, Primary Examiner. STEPHEN J. TOMSKY, Examiner. 

